In Why Humans Like to Cry, Michael Trimble argues that tears of sadness provide a type of joy, that may have co-evolved with tragedy

WE ARE the only animals who shed tears from emotion. But why? And what parts of the brain govern our impulse to weep? In Why Humans Like to Cry, Michael Trimble looks to neuroscience, art and evolution for answers.

His basic argument is that there is a set of neural systems in the brain that respond selectively to emotional stimuli and, specifically, tragedy. By this, he means the individual experience of loss, whose co-evolution with language and culture led to - or at least aided in - the birth of the art form of the same name, which deals with loss and suffering as essential aspects of humanity.

In his close examination of these neural systems and their interconnections, Trimble aims to explain how and when our species became aware of the tragic nature of life, came to cry from emotion, and even to find a kind of pleasure in weeping inspired by tragedy, something he calls "tragic joy".

He begins, boldly, by exploring how Friedrich Nietzsche's conceptions of the Apollonian and Dionysian ways of being apply to the visual and musical arts, respectively. Trimble then uses these as metaphors for the ways psychological processes are rooted in neuroanatomical and evolutionary principles: the Apollonian for the cerebral circuits that underlie conscious reasoning; the Dionysian for the evolutionarily older subcortical circuits that control our emotions.

After a tour of the literature on crying and a detailed assessment of the putative neural circuitry of emotion, he moves on to an exploration of how emotional crying may have evolved. It starts with the bawling of infants, which is not so different from the distress cries of other animals. But we come into the world ready to focus on our mother's face. So begins our lifelong attraction to faces, and the emotions that play across them. Not long after birth, tears begin to accompany crying, and the system that signals our "suffering and pleading for nurture and help" is born.

Trimble uses tragedy to make his case that neural and social phenomena may have co-evolved to produce our, at times, cathartic tears. That is, once we realised that crying provided a sort of solace, we devised ways to prompt this experience on demand.

Our brains cultivate "a special combination of arousal and calm" in response to tragedy, he says. Among the areas of the brain whose activation may prompt tears of tragic joy are the medial and lateral prefrontal cortex - key to the experience of empathy. But Trimble concludes that it is also decreased activation in the more primitive amygdala, associated with fear and strong emotion, that leads tragedy to elicit feelings of empathy and intimacy.

Trimble earned my respect for his erudition and ambition, but I found his ultimate conclusion to be somewhat less than I was expecting. He is, nevertheless, an engaging storyteller. And he may just be correct.

Randolph Cornelius is professor of psychology at Vassar College in New York, and co-editor of Adult Crying (Routledge, 2001)

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